ncx2cdf
"upper")Noncentral chi-squared cumulative distribution function (CDF).
For each element of x, compute the cumulative distribution function (CDF) of the noncentral chi-squared distribution with df degrees of freedom and noncentrality parameter lambda. The size of p is the common size of x, df, and lambda. A scalar input functions as a constant matrix of the same size as the other inputs.
p = ncx2cdf (x, df, lambda, "upper") computes
the upper tail probability of the noncentral chi-squared distribution with
parameters df and lambda, at the values in x.
Further information about the noncentral chi-squared distribution can be found at https://en.wikipedia.org/wiki/Noncentral_chi-squared_distribution
See also: ncx2inv, ncx2pdf, ncx2rnd, ncx2stat, chi2cdf
Source Code: ncx2cdf
## Plot various CDFs from the noncentral chi-squared distribution
x = 0:0.1:10;
p1 = ncx2cdf (x, 2, 1);
p2 = ncx2cdf (x, 2, 2);
p3 = ncx2cdf (x, 2, 3);
p4 = ncx2cdf (x, 4, 1);
p5 = ncx2cdf (x, 4, 2);
p6 = ncx2cdf (x, 4, 3);
plot (x, p1, "-r", x, p2, "-g", x, p3, "-k", ...
x, p4, "-m", x, p5, "-c", x, p6, "-y")
grid on
xlim ([0, 10])
legend ({"df = 2, λ = 1", "df = 2, λ = 2", ...
"df = 2, λ = 3", "df = 4, λ = 1", ...
"df = 4, λ = 2", "df = 4, λ = 3"}, "location", "southeast")
title ("Noncentral chi-squared CDF")
xlabel ("values in x")
ylabel ("probability")
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## Compare the noncentral chi-squared CDF with LAMBDA = 2 to the
## chi-squared CDF with the same number of degrees of freedom (4).
x = 0:0.1:10;
p1 = ncx2cdf (x, 4, 2);
p2 = chi2cdf (x, 4);
plot (x, p1, "-", x, p2, "-")
grid on
xlim ([0, 10])
legend ({"Noncentral χ^2(4,2)", "χ^2(4)"}, "location", "northwest")
title ("Noncentral chi-squared vs chi-squared CDFs")
xlabel ("values in x")
ylabel ("probability")
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